Manually operable press having an emergency unlocking button

Details Manually operable press having an emergency unlocking button Manually operable press having an emergency unlocking button

2000-12-07

2004-06-29

Ostrager, Allen (Department: 3725)

Presses

Safety device

Means to disable or to forestall power to the press

C100S353000, C100S292000, C100S266000

Reexamination Certificate

active

06755124

ABSTRACT:

FIELD OF THE INVENTION
The present invention is related to the field of manually operable presses. More specifically, the invention is related to manually operable presses comprising a manually pivotable actuating lever for effecting a forward press stroke and a return stroke of a press slide or ram, a mechanical return stroke interlock inhibiting a return movement of the press before the press slide has come to a lower end position. Still more specifically, the invention is related to such a press also having a cam plate within the return stroke interlock connected for being pivoted together with the actuating lever, the cam plate having a groove-shaped guide cam provided with a plurality of lock protrusions, a spring-biased lock pin running along the guide cam and being adapted to run freely along the guide ram in an operational direction but being inhibited by the lock protrusions within the guide cam from running in a direction opposite the operational direction.
BACKGROUND OF THE INVENTION
A manually operable press of the kind specified at the outset is disclosed in European patent specification 0 622 175 B1.
Manually operable presses of this kind are mainly used in piecework production lines where the workers are paid according to the number of the processed workpieces. Manually operable presses require to exert a force which increases towards the end of the press stroke. Workers using manually operable presses, therefore, tend to execute the work or press stroke only incompletely and to initiate the relaxation or reverse stroke already prior to having reached the intended lower dead position or end position of the press slide. As a consequence, when the press operation has not been exactly completed, the workpieces must be thrown away or at least have a minor quality.
In order to avoid such consequences, the prior art press according to the European patent specification mentioned above, has a mechanical return stroke lock comprising a cam plate with a groove-shaped control cam and a spring-biased lock pin engaging same. The control cam consists of several sections, two of them extending in a peripheral direction, whereas the third section essentially extends radially and inwardly and a fourth section extending radially outwardly and, along the periphery, back to the first section. Between the first and the second section, there is a lock protrusion which can be surmounted by the lock pin only in a direction from the first towards the second section.
The lock pin itself is spring-biased in an axial direction and is journalled within a sliding block which, in turn, is configured to be moved in a radial direction under the action of a spring.
In the course of the work stroke of the press, the lock pin first runs on the groove bottom from the first to the second section. As soon as the second section has been reached, the worker cannot move the actuating lever again back and upwardly because the lock pin will then come to rest against the lock protrusion which inhibits a further movement of the cam plate being connected for a rotation together with the actuating lever. Only during a further movement of the cam plate along the operational direction and, hence, a movement of the actuating lever downwardly, the rest pin comes into the third cam section and is there moved radially and outwardly together with the sliding block. Only now a return stroke is possible during which the lock pin runs along the fourth cam section in a peripheral direction and radially outwardly, until it again reaches the first cam section.
By doing so, it is guaranteed that the press stroke is first executed completely before the return stroke may be initiated.
However, due to faulty alignment of the workpieces to be pressed together and/or due to wrong workpiece tolerances, it may happen once in a while that the press stroke cannot be executed completely because the lower end position of the press stroke cannot be reached due to the dimensions and/or the orientations of the workpieces with respect to one another. In order to enable discharging of such faulty workpieces, the control cam of the prior art press comprises an arcuate slot being accessible from the outside making the second and the third section of the control cam accessible. If the press is jammed as described before, the lock pin may be pushed back in an axial direction from outside by introducing a thin device through the slot, thus making it possible to rotate the control cam back from that position and letting the lock pin run along the control cam in a direction opposite the operational direction.
Although this prior art press provides an efficient return stroke lock also enabling to unlock same in an emergency situation, this prior art return stroke lock nevertheless comprises a number of disadvantages in connection with the unlocking in an emergency situation.
First, it is disadvantageous to provide a relatively large slot in the groove bottom of the control cam because dirt may penetrate into the return stroke lock, in particular into the control cam. Therefore, it may happen that the control cam will be repleted with dirt, chips etc. over longer periods of time so that at the end the lock pin will be able to surmount the lock protrusion also in a direction opposite the operational direction.
A second disadvantage consists in the fact that unlocking the lock pin by means of a thin device is relatively complicated. For example It happens all the time that the device will slip off the lock pin before the latter has surmounted the lock protrusion so that the unlocking operation must be repeated several times before it is successful. This is of particular disadvantage when the device and/or the lock pin are covered with oil or another lubricant. Such time-consuming unlocking operations, further, do not make sense, in particular in connection with piecework production lines.
Still another significant disadvantage of the prior art unlocking system becomes apparent in a situation where a worker has come between the press ram and the workpiece to be processed with his finger, his hand or a piece of skin and the skin is then jammed and injured during the execution of the press stroke which may result in severe injuries. In particular in such an emergency situation, the unlocking system in the prior art press is very disadvantageous because one has found that the worker in most cases does not have enough patience to carefully locate the lock pin within the slot by means of the thin device in order to unlock same. In most cases the worker will be so nervous and impatient that he will tear his hand out of the press, thus making the injuries still worse.
Bearing the above in mind, it is an object underlying the present invention to improve a press of the kind specified at the outset such that the return stroke lock on the one hand has a very simple design and, on the other hand, may be unlocked quite easily.
SUMMARY OF THE INVENTION
According to the present invention, this object is achieved by a manually operable press comprising a manually pivotable actuating lever for effecting a forward press stroke and a return stroke of a press slide or ram, a mechanical return stroke lock inhibiting a return movement of the press before the press slide has come to a lower end position of the press stroke, a cam plate within the return stroke interlock, connected for being pivoted together with the actuating lever, the cam plate having a groove-shaped guide cam provided with a plurality of lock protrusions, a spring-biased lock pin running along the guide cam and being adapted to run freely along the guide ram in an operational direction but being inhibited by the lock protrusions within the guide cam from running in a direction opposite the operational direction, an opening each provided in the guide cam at the lock protrusions, unlocking pins provided in each of the openings, the pins being adapted to be actuated from outside the press for bringing the lock pin out of engagement with the lock protrusions, thus allowing the lock pin to run in the oppos

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